William fitz Geoffrey de Mandeville (died 1227) was the third Earl of Essex of the second creation from 1216 to his death. He was the second son of Geoffrey fitz Peter and Beatrice de Say and he succeeded his elder brother Geoffrey fitz Geoffrey as earl and inheritor of the Mandeville barony. He was married to Christina, a daughter of Robert Fitzwalter, but died without heirs and the earldom went extinct.